The fabrication of composite structures from fiber reinforcement layers utilizing a resin infusion and curing technique in connection therewith is already known in the art. The use of such a process for fabrication of structures having multilayer cores sandwiched between fiber-reinforced skins, is usually labor intensive for a variety reasons, most notably due to adhesive bonding and plural infusion operations.
In accordance with the present invention, a porous core is fabricated by compacting and heating a thermoplastic coated microballoon type of material. Layers of such cores are then assembled with layers of reinforcing material, such as fiberglass cloth to form a dry multi-layer sandwich layup. The layup is then bonded by reacting while receiving resin by infusion through the porous cores.